Skin is the first line of defense against environmental insults that would otherwise damage sensitive underlying tissue and organs. For example, skin maintains a relatively water-impermeable barrier between an organism and its environment to prevent dehydration. Additionally, skin plays a key role in a person's physical appearance. Generally, most people desire to have younger, healthy looking skin. And to some of these people, the tell-tale signs of skin aging such as thinning skin, wrinkles, and age spots are an undesirable reminder of the disappearance of youth.
Both intrinsic and extrinsic factors can lead to a decline in skin appearance and function. For example, as skin ages naturally, there is typically a reduction in the cells and blood vessels that supply the skin and a flattening of the dermal-epidermal junction, which leads to thinning and general degradation of the skin's barrier function. Additionally, lifestyle choices and exposure to the environment (e.g., ultraviolet radiation, pollution, cigarette smoke, smog, wind, heat, low humidity, harsh surfactants, abrasives) may lead to the premature appearance of age spots and uneven skin tone. As a result, treating the signs of aging in skin has become a booming business in youth-conscious societies. Treatments range from cosmetic creams and moisturizers to various forms of cosmetic surgery.
Numerous agents, both natural and synthetic, are known for use in skin care compositions marketed to treat various skin conditions, especially those associated with aging. One example of a well-known skin care agent is niacinamide, which has been used in the cosmetics industry to provide a variety of skin health benefits. For example, U.S. Pat. No. 5,833,998 discloses the use of niacinamide for regulating the oily/shiny appearance on skin, and U.S. Pat. No. 5,968,528 discloses the use of niacinamide for regulating the signs of skin aging.
Other examples of well-known skin care agents include saccharides (mono and poly), which have also been widely used in the cosmetics industry to provide a variety of skin health benefits. For example, US 2005/0176677 discloses that mono- and polysaccharides derived from plants of the Lemnaceae family provide various skin care benefits. In another example, US 2008/0312169 discloses the use of D-ribose in a cosmetic composition applied to the skin to reduce the length and area of wrinkles and to improve the complexion of the skin.
In some instances, the combination of skin agents such as niacinamide and saccharides have been disclosed in exemplary cosmetic compositions. For example, US 2012/0121534 and U.S. Pat. No. 5,053,230 disclose compositions for promoting the growth of skin cells to improve the appearance of wrinkled skin. The compositions in the '534 application and '230 patent are disclosed as essentially being growth media for stimulating growth or promoting trophism in skin cells. Some of the examples in these publications disclose niacinamide and ribose optimizing the nutritional content of the growth media. However, it was not recognized that combining niacinamide and a suitable saccharide at low pH in a skin care composition can provide improved skin barrier function and skin appearance benefits.
Typically, cosmetic compositions are formulated to have a slightly acidic to neutral pH (i.e., from 4.0-7.0) which is believed to improve the stability of certain ingredients in the composition (e.g., niacinamide, salicylates, and neutralized thickeners). However, formulating a skin care composition at a lower pH (e.g., 1.0-4.0) may bolster the acid mantle of the skin, provide flexibility in other types of skin agents that can be included in the composition, and/or provide an exfoliation benefit. Accordingly, it would be desirable to provide a low pH skin care composition that includes niacinamide and a suitable saccharide for improving skin barrier function and skin appearance.